Fuse Making - Wrapping, Twisting, or Braiding?

[Extrarius]

I'm interested in creating a fuse-making machine, but after seeing so many DIY versions that use exactly the same principle, I'm curious what people think about other designs:

 

All the DIY machines I've seen work using the principle of wrapping a column of powder in threads with very little to hold the "tube" together (nothing prevents the threads from unwinding [at this point]). Most machines then have a second stage that wraps the "tube" a second time in the opposite direction, which does hold the inner part together, but doesn't hold itself together. Finally, either the machine or the maker (as a manual step) coats the fuse in something like nitrocellulose in order to 'cement' everything together and make it water-proof. A representative example of what I've seen out there is http://www.youtube.com/watch?v=mltIUbaRbaU

 

Another string-based construction is rope, in which each of the strings is twisted before being combined, and then they untwist as a mass in a way that leaves them more firmly combined than simply several threads wrapping a core. For example, a simple rope machine is demonstrated at http://www.youtube.com/watch?v=NUHN3q6k24s. Wouldn't twisting the strands make a better fuse, even if it does make the machine very slightly more complicated?

 

Finally, a third construct is weaving/braiding a tube. For example, paracord has an outer woven layer with an inner twisted layer. The out layer is literally a tube, and seems like it would be perfect for strongly holding powder together to form a fuse. Looking around, most "maypole weaving" machines seem very complicated, but I found a site that has a very simple design that is only moderately more complicated than the wrapping machines - http://dzlsevilgeniuslair.blogspot.com/2012/05/braider-with-spool-runners-and-spools.html.

 

Any of these methods seems like it would work with a proper coating, but it seems to me that each one would be better than the previous. Is there any reason a wrapped fuse is better than a braided tubular fuse, or is it only simplicity that drives the creation of wrapping machines instead of braiding machines for fuse-making?

[FlaMtnBkr]

All commercial visco fuse is made like you first describe, works well, and has been used for a long time now. If the fuse is going to be coated, I don't see why it needs to be more complex than the current design. The coating helps hold it together as well as waterproof it and is probably necessary no matter how it is made.

 

I eventually want to make a visco machine and have studied quite a few machines. Both hobby and a Chinese machine. The first type is how I would go as it is well proven. You will still have some tweaking to do to figure out how many turns per inch and a suitable speed to run it while making sure the powder doesn't stop and leave gaps with no powder within the fuse.

 

Many machines use tracer threads to help pull the powder down as well as something to knock or stir the powder. Also mill powder isn't used but a very fine granulate that flows better.

[markx]

All of the visco machine designs that I have seen (the DIY ones at least) have one very limiting obstruction: they use a single motor to drive the whole system. It would be pure incidental luck to get the rpm ratios correct for a perfectly running setup. Plus you would be limited to the particular thread type and thickness vs the nozzle diameters to get a working solution and changing something would mean a mechanical intervention in the form of different gears or pulleys. So instead of fiddling with gears and transmission ratios I just used three motors with individual PWM controls to make a truly universal platform that can be dialed into correct ratios and wanted speed with just the turn of a button. One does not need big motors for the machine, a few W dc @ 12V will work just fine and cost under 10 buck with a PWM module.

 

Some mugshots:

 

http://www.amateurpyro.com/forums/gallery/album/252-visco-machine/

Edited April 10, 2014 by markx

[Arthur]

The Chinese must produce millions of miles of visco so it is worth the effort to put the motor the other side of the wall and use shafts pulleys and belts to get the drive where the machine needs it. Industrially anything vaguely spark producing is kept well away from open hoppers of BP! If the Chinese have used dextrin or cellulose lacquer to bind time fuse or visco, it's only a derivative from the original Bickford Safety Fuse which contained a layer of tar to waterproof the structure and bind all the layers.

[FlaMtnBkr]

I'm not sure I would say it is a derivative. Visco and Bickford act completely different and the tar and NC play fairly different roles.

 

The tar does what you say but you left out the most important function. And that is keeping the flame contained within the fuse so no flame is exposed, or premature ignition, until the flame shoots out the end.

 

And if you have ever seen a piece of visco straight from the machine, you can see it needs something to coat it to hold everything together and give it some durability.

[MrB]

So instead of fiddling with gears and transmission ratios I just used three motors with individual PWM controls to make a truly universal platform that can be dialed into correct ratios and wanted speed with just the turn of a button. One does not need big motors for the machine, a few W dc @ 12V will work just fine and cost under 10 buck with a PWM module.

Very neat. Using brushless engines, and just as a good measure, fit a shield between the engines and the working parts of the machine, and it's golden. Using a set of brushless engines not only removes a fire hazard, but also makes it virtually impossible to wear out. Buy some with replacable bearings, and you really wont ever be able to wear it out. Very simple, smart design.

 

B!

[markx]

These little motors are so cheap that replacing is really no problem. Besides I could most probably wind more fuse with it than I can ever need without even getting close to wearing out one of these suckers As for the shields....I use plastic cups on the motors when running the machine. That prevents any spills entering the motors, but even in the unlikely event of accidental ignition there will be no disaster, since I only use about 3 teaspoonfuls of meal in the hopper and always run the thing outside. The 3 spoonfuls makes about 5m of fuse which is exactly the amount that I can fit on the collection spool without too much increase in diameter that needs to be compensated with lowering of rpm-s. And the length is manageable when coating with rubber glue. I find diluted rubber glue vastly superior to NC laquer.....dries quicker, leaves a very flexible fuse and you can wind it into a roll without leaving it to dry out completely. It will not stick so strong that you will damage the fuse when unwinding....just enough to keep the roll together. Oh yeah, and it burns underwater just fine

[Arthur]

I think take up spools can be made varispeed with some felt pads to slip under load.

[dave321]

its about time someone should make a visco machine / kit for sale
I'm sure there would be takers

[Bobosan]

That's a sweet looking machine markx and the final product looks very well done. Congrats!

[Arthur]

If there is a trade supplier of visco anywhere near you then it's not worth the effort to make your own, if there is NOT then it's a simple project. Yes I suspect that really with a mechanical machine one would need to derive the settings for one size of visco, but with a digitally controlled one all sizes should be possible.

[markx]

If there is a trade supplier of visco anywhere near you then it's not worth the effort to make your own, if there is NOT then it's a simple project. Yes I suspect that really with a mechanical machine one would need to derive the settings for one size of visco, but with a digitally controlled one all sizes should be possible.

For sure it is not worth the hassle if you can buy it with bargain prices from a vendor and are not interested in making your own. From the standpoint of money you will not win by any means when rolling your own. In fact the most expensive component and a shortlived one in this application is the thread. I was really astonished what even medium quality thread costs these days....it's outrageous. Forget about sewing thread on small rolls, the only option is to buy bulk spools and rewind onto smaller spools for the machine.

But I made the machine just because I enjoyed the process and the result. Money has no vote when it comes to something I do with passion. And the fact that it produces a nice functional fuse is just a bonus

[markx]

A traversing system for the collection spool has become a real neccessity....it's just a pita to sit by the machine and guide the fuse as it piles up. So this is the simplest design that I came up with...it will not traverse the fuse completely uniformly, but I believe it will be giant improvement on the current "hands on" situation.

 

Basically the idea is to attach a crank to a low rpm (below 1rpm) motor and rotate it. The crank has a small ball bearing attached to the end....a fuse guide is attached to the center of the bearing. The center with the fuse guide is free to rotate around it's own axis, so the circular motion of the crank is transformed into a linear misplacement of the fuse with recpect to the center of rotation. If the rotation speed is constant the traversing action will not be uniform throughout the lenght if the misplacement axis...the crank will spend more time at the extremities of the misplacement when compared to the center. Maybe a rough illustration will clarify things : )

 

 

[MrB]

I'm going to suggest something that might be very, very stupid...Get a fishing reel, and replace the crank with a pully. Make sure there is enough play in things to let it slip, and set the brake to it's lowest setting. That way you need to be "almost right" on the drive speed for the thing. Get a used one, they are cheap, and if you get a high capacity one you should be able to fit a nice amount of fuse on it. I don't really think it's an issue, they are well sealed, but if you have the option, get a unit with a magnetic brake over a friction based one.

Hell, get one of those digital ones, you can set the "line" thickness on, and it will keep count of how much you winded home to...

B!

[markx]

I'm going to suggest something that might be very, very stupid...Get a fishing reel, and replace the crank with a pully. Make sure there is enough play in things to let it slip, and set the brake to it's lowest setting. That way you need to be "almost right" on the drive speed for the thing. Get a used one, they are cheap, and if you get a high capacity one you should be able to fit a nice amount of fuse on it. I don't really think it's an issue, they are well sealed, but if you have the option, get a unit with a magnetic brake over a friction based one.

Hell, get one of those digital ones, you can set the "line" thickness on, and it will keep count of how much you winded home to...

B!

Hah! That's an excellent idea! A ready made unit with traversing action....just connect to a suitable motor and dial in the rpm-s

[schroedinger]

Why not just use a small drumm with a large bore diameter. So could the fuse assemble itself without any problems.

[MrB]

Not actually having made any visco machines, it's hard to say, but it's my understanding that you need to keep some tension on the fuse as it wont feed properly other-ways. I guess you could add a constant drive, something like a pair of rubber wheels with a small grove in them, so it just grab, but doesn't squeeze the fuse much, and from there drop it in a bucket...

B!

[markx]

Why not just use a small drumm with a large bore diameter. So could the fuse assemble itself without any problems.

True....but I love building things too much to let a simple intrinsic stacking routine solve this situation Besides I've already built the crank mechanism...only waiting for the drive motor to arrive from ebay.

 

 

Not actually having made any visco machines, it's hard to say, but it's my understanding that you need to keep some tension on the fuse as it wont feed properly other-ways. I guess you could add a constant drive, something like a pair of rubber wheels with a small grove in them, so it just grab, but doesn't squeeze the fuse much, and from there drop it in a bucket...

B!

Yes...keeping the tension is vital for consistant operation, but the uncoated fuse actually retains so much twisting torque from the winding actions that releasing it from a "wire feeder" into a receptacle is going to produce a tangled mess that is quite hard to unravel. Therefore collecting it on a spool is a more elegant option.

[markx]

Allrighty....my 2rpm motor arrived today! I will be completing the traverser for the visco machine coming weekend and upload the chronicles

[markx]

Right....as promised the traversing mechanism is completed and works like a charm. See the pics attached:

 

The only problem is that I need to include a resistor of suitable ohmic value to slow down the traverser. Currently it just travels too quickly and winds the fuse in a very loose pattern....but performs it's task nevertheless

 

Video evidence:

 

http://youtu.be/ZnMqOF28STM

Edited May 19, 2014 by markx

[FlaMtnBkr]

So your machine doesn't put 2 layers of thread wrapping? One opposing the other?

[MrB]

It does. Look at pics in the first post, and also, in this last post you can see the string coming from the above if you look closely.

B!

[markx]

Yes the machine winds in the usual manner....two layers in opposite directions.

I tend to have a cosmetic problem with the fuse that the machine produces, it seems that the winding torque in the braid has no means to release itself and tends to twist the fuse into a helix shape. Not a problem for functionality, but the appearance suffers from the irregularity. The first 40cm (distance between upper plate and guide wheel) of fuse are utterly perfect because the unfilled portion of the braid allows the torque to relax until it passes the guide wheel before the traverser. After the filled portion reaches the guide wheel, the torque in the braid begins to build up and starts twisting the fuse into a helix.....altering the rpm-s or the thread feed resistance of the winding stages has practically no effect on the matter. Anyone have any ideas on how to correct this problem?

[MrB]

Since the torque is created by one of the winds, shouldn't increasing the tension on the strings of the other one fix the issue? Perfectly balanced the result shouldn't want to twist at all, but i suppose that level of accuracy might be hard to get. Also, string winding tension seams to be set by a combination of the die shape, and the bobin weight. So as thread is used, the spool gets lighter, and tension drops... Consistency may, or may not be an issue. One way to deal with that is having all the spools equipped with different length thread, but that means you have to nurse the machine, stop it, replace empty threads, and so on, all the time.

 

I think i would have started with figuring out which wind is causing the torque. I think it might be the second one, and if thats the case, fewer threads, or lighter spools might be the way to go.

Does it affect fuse performance? If not, ignore it, shouldn't be an issue once you coat it with NC... Just keep it somewhat tensioned while drying.

 

Another way to deal with it could be like some fuse machines do. Add a layer of paper between the wraps. I think it lets you get away with a "loser" outer wrapping, as well as stiffens up the fuse countering torque mess. But i have no idea where to get paper suitable for it...

B!

[markx]

Since the torque is created by one of the winds, shouldn't increasing the tension on the strings of the other one fix the issue? Perfectly balanced the result shouldn't want to twist at all, but i suppose that level of accuracy might be hard to get. Also, string winding tension seams to be set by a combination of the die shape, and the bobin weight. So as thread is used, the spool gets lighter, and tension drops... Consistency may, or may not be an issue. One way to deal with that is having all the spools equipped with different length thread, but that means you have to nurse the machine, stop it, replace empty threads, and so on, all the time.

 

I think i would have started with figuring out which wind is causing the torque. I think it might be the second one, and if thats the case, fewer threads, or lighter spools might be the way to go.

Does it affect fuse performance? If not, ignore it, shouldn't be an issue once you coat it with NC... Just keep it somewhat tensioned while drying.

 

Another way to deal with it could be like some fuse machines do. Add a layer of paper between the wraps. I think it lets you get away with a "loser" outer wrapping, as well as stiffens up the fuse countering torque mess. But i have no idea where to get paper suitable for it...

B!

Thanks for the reply and helpful suggestions

It's the first layer that causes the torque twist.....I attached resistance dies for each separate string on the first plate to increase the tension and straighten out the helix, but to no avail. I'm using thicker threads on the first layer to catch more powder into the core and provide a complete coverage, the second top layer is very thin tread just to cover up and seal the first without increasing the diameter to noticeable extent. I think it might actually be the particular inner core threads in combination with the mechanics of the machine that cause this effect, because at first I used even thicker high quality threads on the first layer and I had no twisting or deforming. But then I switched to the thread that I use now for reasons of economy and the problems began